This is the last in a series of posts by Craig Anderson describing the off-the-grid house he built with his wife France-Pascale Ménard near Low, Québec. Craig writes about the "Seven Hills Project" in a blog called Sunshine Saved. For a list of Craig's previous posts, see the list of "Blogs by Craig Anderson" in the sidebar below.

I recently investigated an attic with spray foam insulation where we observed an interesting humidity pattern. We placed data loggers near the ridge and floor of the attic as well as in the living space and outdoors.

The graph at below shows dew point data for the four locations. The really interesting part is the big difference in dew point between the highest and lowest points in the attic, shown by the red and green curves in the graph.

Among the most interesting exhibitors at the GreenBuild International Conference and Expo, an event held in early October in Los Angeles, may have been the Asphalt Pavement Alliance, a group that challenged what we thought we knew about the urban heat-island effect with peer-reviewed research from Arizona State University (ASU).

Ben Rush likes the idea of a ground-source heat pumpHome heating and cooling system that relies on the mass of the earth as the heat source and heat sink. Temperatures underground are relatively constant. Using a ground-source heat pump, heat from fluid circulated through an underground loop is transferred to and/or from the home through a heat exchanger. The energy performance of ground-source heat pumps is usually better than that of air-source heat pumps; ground-source heat pumps also perform better over a wider range of above-ground temperatures., despite their reputation for higher cost than other heating and cooling alternatives.

A ground-source heat pump (GSHPs) requires heat-exchange tubing buried in the ground or inserted in a well or pond. The excavation required to bury the lines (or drill an extra well or two) helps to make GSHPs more expensive than air-source units. In addition, the equipment itself tends to be more costly. In all, GSHPs suffer a significant disadvantage when it comes to cost.

Just about every week, I get a call or an email that turns into a building science puzzle. While the problems are varied, how you solve them doesn’t change.

First, you understand how heat and moisture move through building assemblies. Second, you follow the advice of your spouse.

My wife of 27 years is a real master at jigsaw puzzles, and she would laugh to learn that I think of myself as a puzzle master of any sort, since I am useless at the jigsaw ones. But she completely agrees that I should use her method of solving jigsaw puzzles in my work on building science problems.

If you’ve been puzzled by the proliferation of "net," "nearly" and "almost ready" zero-energy definitions and standards and have wondered just how net or nearly they truly are, take heart. The PassivhausA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates. Institut (PHI) has introduced an equitable assessment of energy use to help guide us toward the 100% renewable energy future we must rapidly achieve.